The present application relates generally to a power combiner and splitter apparatus, and methods of operating the same. In particular, it relates to a radio frequency (RF) power combiner and splitter circuitry.
A power combiner is typically used to receive electric signals at a plurality of input ports and generate a combined signal at a common port. A power splitter, also referred to as a divider, is typically used to receive an electric signal at a common port and generate a plurality of signals at a plurality of output ports. Power combiners and splitters are commonly used as components for handling radio frequency (RF) signals. A combiner/splitter may have one common port that serves as input for the splitter and output for the combiner, and a plurality of input/output ports that serve as outputs ports for the splitter, and inputs for the combiner.
One known power combiner/splitter architecture is the Wilkinson power combiner/splitter. FIG. 1A is a schematic diagram illustrating a two-way Wilkinson power combiner/splitter 100, while FIG. 1B shows its corresponding s-parameter matrix. Combiner/splitter has a common port P1, two input/output ports P2 and P3, and quarter wave elements 102 coupled between P1, P2 and P3. The input/output ports P2 and P3 are coupled with a resistor 104 having an impedance value of 2Z0. As a combiner, combiner/splitter 100 combines equal phase signals applied at the input ports P2, P3 into one signal at common port P1. As a splitter, combiner/splitter 100 splits the input signal at common port P1 into two equal phase and equal power signals at output ports P2, P3. Quarter wave (λ/4) element 102 may also be referred to as a 90° phase shift element and is configured to cause a 90° phase shift in a transmitted radio frequency signal. Quarter wave elements 102 may be transmission lines with characteristic impedance Z=√{square root over (N)} Z0 and length λ/4, where λ is the wavelength of the electromagnetic wave propagating in the circuit, Z0 is a characteristic impedance of the RF system connected to the P1, P2 and P3, and N is the number of input/output ports, or using lumped LC circuits which are equivalent to the transmission line with characteristic impedance √{square root over (N)} Z0 and length λ/4.
One advantage of the Wilkinson combiner/splitter is that all the ports are impedance matched and there is isolation between the input/output ports P2, P3 from the resistor 104. In an ideal Wilkinson splitter/combiner there is no power loss due to reflections and there is no power lost in the resistor 104 between P2 and P3.
FIG. 2A is a schematic diagram illustrating a generalized N-way Wilkinson power combiner/splitter 200, while FIG. 2B shows its corresponding s-parameter matrix. The N input/output ports P2 and P3 are each coupled with the common port P1 via quarter wave elements 102. Each input/output port is also coupled to each one of the rest of the input/output ports via resistors 204 having an impedance value of Z0, where there are two resistors 204 serially connected in between a pair of input/output ports. Power combiner/splitter 200 works similarly to the 2-way power combiner/splitter 100, and has the advantage of matching for all ports and complete isolation between the N input/output ports P2, P3, . . . , PN+1. Therefore, for an ideal case there is no power loss due to reflections and there is no power lost in the resistors 204.